NZ214483A - Sealing system for regulator valves of pressure reducing valve - Google Patents

Description

2144S3 Tlj : ,r:,^ •irife*-!?..!.'.?- ; N.Z.No.

NEW ZEALAND Patents Act 3953 COMPLETE SPECIFICATION " 5CAA-J»JC. SYSTEM foR VujOT VALVES o r PRESSURE REDUCING VALVE" We, TLV COMPANY, LIMITED, of 8th Floor Hibiya Kokusai Building, 2-3, Uchisaiwai-cho 2-chome, Chiyoda-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a Patent may be granted to us , and the method by which it is to be performed, to be particularly described in and by the following statement : - - 1 - (followed by 1A) 2L4483 SPECIFICATION This invention relates to a pilot-type pressure reducing valve used in a piping system of steam, compressed air or the like, for maintaining secondary fluid pressure at a predetermined set value and, especially, to improved sealing means used in a slide portion of a plunger structure interlocked with a main or pilot valve for controlling it.

As described, for example, in the Japanese utility a.(fouo'itati*. on wqvwl-) model publication No. 45-271841, a pilot-type pressure reducing valve includes a pilot valve, in addition "to a main valve, disposed in a fluid path communicating the primary side of the main valve with a cavity above a piston interlocked with the main valve for controlling it. The pilot valve is controlled, as described later, by a diaphragm which deflects in response to fluid pressure in the secondary side of the main valve, to control the amount of fluid flowing into the above cavity, thereby driving the piston and the main valve interlocked therewith in accordance with a pressure difference between the upper surface of the piston and its bottom surface which is in the secondary orfww»oUe»«. otmacphara.

A pressure reducing valve of this type includes such piston and pilot valve which effect delicate motion in accordance with the primary and secondary sides, as described above, and substantially influence wpan the operational characteristics of the valve itself. More specifically, as to the piston, the fluid pressure acting to the upper surface thereof is controlled by leaking the primary fluid having flowed into the cavity above the piston through the pilot valve, through a gap between the piston and cylinder.

If this gap is small, the leakage of fluid is also small and KMoioina open this may result in the main valve laft at oponod and/or the piston burnt -to the cylinder. If the gap is widened enough -1 214483 to pr&vent such ifwfcic »f burning seizure, the leakage will CtnJi become large reduce the force for driving the main valve. As for the pilot valve, if the primary fluid flows through a gap between a pilot stem and a stem guide into a cavity under a diaphragm (hereinunder referred to as "diaphragm chamber"), the pressure in the diaphragm chamber, which has initially to be the secondary pressure, varies and, consequently, the diaphragm whose operation is subject to thio this pressure may operate erroneously. If the gap is made 10 narrower to prevent the leakage, however, the increased slide resistance will disturb smooth motion thereof. Thus, it is desired to provide such slide portion with a structure having high sealing power and low slide resistance.

In order to attain the above object, in the above-15 cited Japanese publication, a fixed gap is formed between the piston and cylinder and a metal ring is disposed in an annular groove formed in the side wall of the piston to dbovt a allow the fluid abob« the piston to leak through tfce gap between the metal ring and the cylinder.

However, such structure may result in unstable motion of the slide portion, which causes erroneous operation as a whole. More specifically, the metal ring, which is made typically of phosphorus bronze, gives non-uniform leakage j between the metal ring and the inner cylinder surface due to irregularity of its outer diameter, and sometimes causes I; j seizure of the slide portion due to thermal expansion, which jj may result in erroneous operation. Accordingly, it has s become necessary to substitute the phosphorus bronze ring •! !! with another ring having low elastic force and low contac.t 30ii resistance.

Accordingly, an object of this invention is to provide an improved structure of pressure reducing valve having its slide portion modified to exhibit high sealing power and low sliding resistance and to avoid seizure du^ to thermal expansion. .1 •"A, n * a t ^ > According to this invention, there is provided a pressure reducing valve comprising a main valve and a pilot valve for controlling said valve, each said valve including a plunger structure comprising a movable inner member having a cylindrical outer surface and a stationary outer member having a cylindrical inner surface facing said outer surface of said inner member, characterized in that said inner member has at least two spaced apart sealing means, each said means containing at least one annular sealing member and said sealing member being made of low-friction material and at least partially axially s p]i t.

In practice, the first and second members may be piston and cylinder, respectively, for controlling the main valve, or pilot stem and stem guide, respectively, for controlling the pilot valve.

The above and other features and effects of this invention will be described in more detail below with reference to the acompanying drawings.

In the drawings: Figure 1 is a sectional side view of a pressure reducing valve in which the invention is embodied; Figure 2 is an enlarged partially sectional side view of a piton-cylinder structure of the pressure reducing valve of Figure 1; and Figure 3 is an enlarged sectional view of a pilot valve structure of the pressure reducing valve of Figure 1.

Throughout the drawings, some reference numerals are given to corresponding structural components.

Referring to Figure 1, an embodiment of pressure reducing valve according to this invention includes a trap body 29 having a bottom cover 31 containing a float 34, a main body 1 containing a piston 6, a cylinder 9, a OCT i9S7 o m! 21448 main valve 5 and a separator structure including swirl vanes 27 and a drain member 28, a pilot body 32 containing a pilot valve 11, and a spring casing.33 containing a pressure setting spring 14. These components are coupled in this order, as in the drawing, by their flanges with suitable disposed therebetween. A diaphragm is disposed between pilot body 32 and spring casing 33.

The main body 1 has an inlet port 2 and an outlet port 3 formed coaxially with each other and connected mutually through a valve port 4. The main valve 5, which is urged upwards by a spring against a valve seat formed around the valve port 4, has a central pin extending upwards and butting within valve port 4 against the bottom end of a piston pin extending downwards from piston 6.

The pilot valve 11 is disposed between a communication r to** fot Z hole 12I^Mp—a—cavity under main valve—5 and another communication hole 13 a cavity above piston 6, and urged upwards by a spring against diaphragm 15. On the other hand, the diaphragm 15 is urged nTlflrouglT*a spring pad 23 by means of pressure setting spring 14 whose compressive force can be adjusted by an adjusting screw 22. A chamber under diaphragm 15 (that is, diaphragm chamber) is connected through a communication hole 26 to outlet port 3, while a chamber above diaphragm 15 is connected through a communication hole 25 to the external atmosphere.

The drain member 28 is disposed with a screen within the space under the valve port 4. The drain member 28 includes two coaxial cylindrical members, the inner one of which has its lower end expanded, and a plurality of swirl vanes 27 are arranged between the inner and outer members.

Within the trap body 29, a hemispherical float cover 35 having a plurality of through holes 36 is supported over the bottom plate 31 by suitable means, not shown, and a hollow spherical float 34 is contained freely within the space between cswscr 35 and bottom plate 31. The bottom 2L4483 * plate 31 has a drain port 37 provided with a drain .valve 3 seat 38 which is normally closed by the float 34 las a valve A jbody. j In operation, the main valve 5 is normally closed by 9 a spring force acting upwards thereon and the pilot valve 11 is normally opened by a preset downward spring force of pressure setting spring 14 adjusted previously by adjusting vbpour screw 22. When a steam flow containing vater fume comes in I jj the inlet port 2, its pressure is conducted through communi-10 1 cation hole 12 to the cavity under pilot valve 11 and then to the cavity above piston 6 through the opened pilot valve 11 and communication hole 13, to pushTpistonldownwards, thereby opening the main valve 5. Thus, the steam comes in | the trap 29, passes through the opened main valve 5 and then 15 ' comes out of the outlet port 3. During this passage of J steam, the swirl vanes 27 swirl the steam to separate the l| water by centrifugal force to cause it Ipool in the li I bottom of trap 29 as drainage. When the drainage is accumulated enough to overcome the weight of float 34, the float j 34 leaves the valve seat 38 to discharge the drainage from | drain port 37. h m, » jj If the steam pressure Irises above a preset value, it , is conducted through communication hole 26 to the diaphragm : chamber to push the diaphragm 15 against the spring 14. 25 : This results in closure of pilot valve 11 urged upwards by a . spring as shown and consequent balance in pressure between * # the upside and underside of piston 6 due to leakage through ; an orifice 10 (Fig. 2) of piston 6. Accordingly, main 1 valve 5 is closed by the spring force backed up by the steam 'I pressure in the primary side, to stop the steam flow.

The same operation is repeated with Tvlfriation in the primary steam pressure to regulate its secondary pressure at the preset value . /s;. j Figure 2 shows the piston structure according to this invention. The structure includes a piston cylinder 9 and a & e^y 214483 a piston 6 inserted into the cylinder 9 leaving a small gap therebetween. The piston 6 has an orifice 10 for connect-;. ing its upside and underside for the abovementoned purpose. ro*'iolly Two annular grooves 61 are formedlapart from each other in j) fi'shxi 53 the eyliwdgiaal outer wall and an annular ring-shaped sealing I J member 8 is fit in each groove 51. The sealing member 8 is made of fluorine resin and a^partod at least at a part 62. A leaf spring 7 is disposed between the sealing member 8 and the bottom of groove 61 to urge the sealing member 8 against 10^ the inner surface of the cylinder 9 in order to assure an intimate contact therebetween.

Referring next to Figure 3, the pilot valve structure 11 (Fig. 1) according to this invention comprises a stem guide 16 and a pilot stem 17 inserted into a guide hole 161 15* of the latter. A valve seat 162 is formed around the lower end of the guide hole 161 for contact with a valve body 21 of pilot stem 17. Intersecting the guide hole 161, a holi-j zontal through-hole 18 is formed in the stem guide 16 and -• j connected to communication hole 13 (Fig. 1) for the above- n 20. mentioned purpose.

I The pilot stem 17 is composed of a spindle 171 with a diameter substantially less than the inner diameter of guide hole 161 of stem guide 16. The spindle 171 has a flange- -|like enlarged portion 172 formed integrally therewith just -25 above the through-hole 18, a valve body 21 fixed to the lower •jj end and a tojD^nember 173 prooo fit on the top and a sleeve 20 slidably 4-*4: on the spindle 71 between both elements 172 d •i and 173. The elements 20, 172 and 173 has a diameter slightly less than the inner diameter of the guide hole 161. Bet- ^ ween the elements 20 and 172 and the elements 20 and 173, a 1 pair of annular sealing members 19 are disposed respectively. Each member 19 is made of fluorine resin and slfp'aratod ■at laact-at—a partll91. The axial dimension of the elements X 19 and 20 are designed so that the sum of them is less than 3$J the spacing between the elements 172 and 173 and substantial x. 1 " ^ 214483 I axial movement of the elements 19 and 20 is allowed. Such design enables absorption of possible thermal expansion of the sealing members 19 in both axial and radial directions to prevent the aforementioned problem of seizure. On the top member 173. a domed cap 24 is for contact with the diaphragm 15 (Fig. 1).

As described above, the sealing members 8 and 19 made of fluorine resin and separated at—least at—a part—(63 ,—161-) ;I?nf thofoe 4\ accordance with this invention exhibit substantially reduced slide resistance and effectively absorb their cvtriot thermal expansion, if any, and their amal separation on end each'piston 6fe* pilot stem 17 am avoid*any inclination thereof which may result in non-uniform contact, thereby maintaining constant smooth operation of the valve.

It should be noted that the above description has been made for explanation purpose only and various modifications and changes can be made within the scope of this invention offtwro as set forth in the apondod claims.

-Ua.

Claims (8)

WHAT WE CLAIM IS:

1. A pressure reducing valve comprising a main valve and a pilot valve for controlling said valve, each said valve including a plunger structure comprising a movable inner member having a cylindrical outer surface and a stationary outer member having a cylindrical inner surface facing said outer surface of said inner member, characterized in that said inner member has at least two spaced apart sealing means, each said means containing at least one annular sealing member and said sealing member being made of low-friction material and at least partially axially split.

2. A pressure reducing valve according to claim 1 wherein said low-friction material is ethylene fluoride or po 1 y-tet rafluorethylene.

3. A pressure reducing valve according to claim 1 or 2 characterized in that the inner member of at least the main valve has at least two spaced apart annular grooves on the outer surface thereof, each said groove containing one of the sealing means.

4. A pressure reducing valve according to claim 3 characterized in that an elastic member is disposed between the bottom of said groove and said sealing member, thereby urging said sealing member against the inner surface of said outer member. /', C 8 1 OCT1987£ / // r, * -i ,1 ~ > faj- I - O v-J

5. A pressure reducing valve according to claim 3 or 4 characterized in that said elastic member is an annular leaf spring.

6. A pressure reducing valve according to any one of claims I to 5 characterized in that each said inner member is a piston and each said outer member is a cylinder, said piston of at least the main valve including an orifice connecting both sides thereof.

7 . A pressure reducing valve according to any one of Lhe claims 1 to 5 characterized in that said inner member of the pilot valve is a pilot stem and said outer member is a stem guide, said pilot stem having a diameter reduced over an intermediate portion thereof leaving it unchanged at both side portions of said intermediate portion, a cylindrical sleeve being slidably fitted on said intermediate portion, and said sealing members being disposed around said intermediate portion between said sleeve and said both side portions having the unchanged diameter as to permit some axial and radial clearance.

8. A pressure reducing valve substantially as herein described with reference to the accompanying drawings. TLV COMPANY, LIMITED By their attorneys HENRY HUGHES LIMITED